Lightning strikes the Willis Tower (formerly Sears Tower) in downtown on June 12, 2013 in Chicago, Illinois. (Photo by Scott Olson/Getty Images)

Sea lion “Jay” paints a Chinese character reading “the Serpent” at the Hakkeijima Sea Paradise aquarium in Yokohama, suburban Tokyo on January 3, 2013. The event, marking the forthcoming Chinese lunar calender year of the snake was held as part of a New Year's attraction. (Photo by Kazuhiro Nogi/AFP Photo)

An Afghan National Army (ANA) soldier assigned to the Mobile Strike Force Kandak fires a RPG-7 rocket-propelled grenade launcher during a live-fire exercise supervised by the Marines with the Mobile Strike Force Advisor Team on Camp Shorabak, Helmand province, Afghanistan, May 20, 2013. The Marines with the Mobile Strike Force Advisor Team instructed and mentored their ANA counterparts on how to properly utilize their weapons systems. (Photo by SSgt Ezekiel R. Kitandwe/RCT 7)

The Porsche 919 Hybrid No17 of the Porsche Team driven by Timo Bernhard of Germany is seen in action during the 83rd 24-hour Le Mans endurance race, in Le Mans, western France, Saturday, June 13, 2015. (AP Photo/David Vincent)

Yang Shiguang, 77, performs stunts at a park in Xi'an, Shaanxi province, September 3, 2013. Yang has been a member of a stunt performance club since 2007, after retiring from a research institution. (Photo by Reuters/China Daily)

An Alitalia plane approaches to land as starlings fly at Fiumicino international airport in Rome October 14, 2013. Italy will have to notify a planned government-led 500-million-euro bailout of near-bankrupt airline Alitalia to EU regulators who will then assess whether the measure complies with EU state aid rules, the European Commission said on Monday. (Photo by Max Rossi /Reuters)

Mr. Zhong Hua, of Johns Hopkins University School of Medicine, took this image of the peripheral nerves (those outside of the brain) in an 11.5-day-old mouse embryo, magnified five times. (Photo by Zhong Hua)